Active Galactic Nuclei Research Articles

PICZL : Image-based photometric redshifts for AGN

Computing reliable photometric redshifts (photo-z) for active galactic nuclei (AGN) is a challenging task, primarily due to the complex interplay between the unresolved relative emissions associated with the supermassive black hole and its host galaxy. Spectral energy distribution (SED) fitting methods, while effective for galaxies and AGN in pencil-beam surveys, face limitations in wide or all-sky surveys with fewer bands available, lacking the ability to accurately capture the AGN contribution to the SED, hindering reliable redshift estimation. This limitation is affecting the many tens of millions of AGN detected in existing datasets, such as those AGN clearly singled out and identified by SRG/eROSITA. Our goal is to enhance photometric redshift performance for AGN in all-sky surveys while simultaneously simplifying the approach by avoiding the need to merge multiple data sets. Instead, we employ readily available data products from the 10th Data Release of the Imaging Legacy Survey for the Dark Energy Spectroscopic Instrument, which covers > 20,000 deg of extragalactic sky with deep imaging and catalog-based photometry in the grizW1-W4 bands. We fully utilize the spatial flux distribution in the vicinity of each source to produce reliable photo-z. We introduce PICZL a machine-learning algorithm leveraging an ensemble of convolutional neural networks. Utilizing a cross-channel approach, the algorithm integrates distinct SED features from images with those obtained from catalog-level data. Full probability distributions are achieved via the integration of Gaussian mixture models. On a validation sample of 8098 AGN PICZL achieves an accuracy $ NMAD $ of 4.5<!PCT!> with an outlier fraction eta of 5.6<!PCT!>. These results significantly outperform previous attempts to compute accurate photo-z for AGN using machine learning. We highlight that the model's performance depends on many variables, predominantly the depth of the data and associated photometric error. A thorough evaluation of these dependencies is presented in the paper. Our streamlined methodology maintains consistent performance across the entire survey area, when accounting for differing data quality. The same approach can be adopted for future deep photometric surveys such as LSST and Euclid, showcasing its potential for wide-scale realization. With this paper, we release updated photo-z (including errors) for the XMM-SERVS W-CDF-S, ELAIS-S1 and LSS fields.

Effects of ultrafast outflows on X-ray time lags in active galactic nuclei

The time lag between soft (e.g., $0.3 1$\,keV) and hard (e.g., $1 4$\,keV) X-ray photons has been observed in many active galactic nuclei (AGNs) and can reveal the accretion process and geometry around supermassive black holes. High-frequency Fe K and soft lags are considered to originate from the light-travel distances between the corona and the accretion disk, while the propagation of the inward mass accretion fluctuation usually explains the low-frequency hard lags. Ultrafast outflows (UFOs) with a velocity range of $ 0.3$c have also been discovered in numerous AGNs and are believed to be launched from the inner accretion disk. However, it remains unclear whether UFOs can affect the X-ray time lags. As a pilot work, we aim to investigate the potential influence of UFOs on X-ray time lags of AGNs in a small sample. By performing the UFO-resolved Fourier spectral timing analysis of archival XMM-Newton observations of three AGNs with transient UFOs -- PG 1448+273, IRAS 13224-3809, and PG 1211+143 -- we compare the X-ray timing products, such as lag-frequency and lag-energy spectra, of observations with and without UFO obscuration. Our results find that in each AGN, low-frequency hard lags become weak or even disappear when they are accompanied by UFOs. This change is confirmed by Monte Carlo simulations at a confidence level of at least $2.7 In the high-frequency domain, soft lags remain unchanged, while the Fe K reverberation lags tentatively disappear. The comparison between timing products of low- and high-flux observations on another three AGNs without UFOs (Ark 564, NGC 7469, and Mrk 335) suggests that the disappearance of low-frequency hard lags is likely related to the emergence of UFOs, not necessarily related to the source flux. The presence of UFOs can affect X-ray time lags of AGNs by suppressing the low-frequency hard lags, which can be explained by an additional time delay introduced by UFOs or disk accretion energy, which should transferred to heat the corona, carried away by UFOs.

Accelerated formation of ultra-massive galaxies in the first billion years.

Recent James Webb Space Telescope (JWST) observations have revealed an unexpected abundance of massive-galaxy candidates in the early Universe, extending further in redshift and to lower luminosity than what had previously been found by submillimetre surveys1-6. These JWST candidates have been interpreted as challenging the Λ cold dark-matter cosmology (where Λ is the cosmological constant)7-9, but, so far, these studies have mostly relied on only rest-frame ultraviolet data and have lacked spectroscopic confirmation of their redshifts10-16. Here we report a systematic study of 36 massive dust-obscured galaxies with spectroscopic redshifts between 5 and 9 from the JWST FRESCO survey. We find no tension with the Λ cold dark-matter model in our sample. However, three ultra-massive galaxies (logM★/M⊙ ≳ 11.0, where M★ is the stellar mass and M⊙ is the mass of the Sun) require an exceptional fraction of 50 per cent of baryons converted into stars-two to three times higher than the most efficient galaxies at later epochs. The contribution from an active galactic nucleus is unlikely because of their extended emission. Ultra-massive galaxies account for as much as 17 per cent of the total cosmic star-formation-rate density17 at redshifts between about five and six.

Nuclear burning in an accretion flow around a stellar-mass black hole embedded within an AGN disk

Abstract A stellar-mass black hole, embedded within the accretion disk of an active galactic nuclei (AGN), has the potential to accrete gas at a rate that can reach approximately ∼109 times the Eddington limit. This study explores the potential for nuclear burning in the rapidly accreting flow towards this black hole and studies how nucleosynthesis affects metal production. Using numerical methods, we have obtained the disk structure while considering nuclear burning and assessed the stability of the disk. In contrast to gas accretion onto the surface of a neutron star or white dwarf, the disk remains stable against the thermal and secular instabilities because advection cooling offsets the nuclear heating effects. The absence of a solid surface for a black hole prevents excessive mass accumulation in the inner disk region. Notably, nuclear fusion predominantly takes place in the inner disk region, resulting in substantial burning of $\rm ^{12}C$ and $\rm ^{3}He$, particularly for black holes around M = 10 M⊙ with accretion rates exceeding approximately ∼107 times the Eddington rate. The ejection of carbon-depleted gas through outflows can lead to an increase in the mass ratio of oxygen or nitrogen to carbon, which may be reflected in observed line ratios such as $\rm N\, V/C\, IV$ and $\rm O\, IV/C\, IV$. Consequently, these elevated spectral line ratios could be interpreted as indications of super-solar metallicity in the broad line region.

AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system

With a growing number of facilities able to monitor the entire sky and produce light curves with a cadence of days, in recent years there has been an increased rate of detection of sources whose variability deviates from standard behavior, revealing a variety of exotic nuclear transients. The aim of the present study is to disentangle the nature of the transient AT\,2021hdr, whose optical light curve used to be consistent with a classic Seyfert 1 nucleus, which was also confirmed by its optical spectrum and high-energy properties. From late 2021, AT\,2021hdr started to present sudden brightening episodes in the form of oscillating peaks in the Zwicky Transient Facility (ZTF) alert stream, and the same shape is observed in X-rays and UV from Swift data. The oscillations occur every sim 60-90 days with amplitudes of sim 0.2 mag in the g and r bands. Very Long Baseline Array (VLBA) observations show no radio emission at milliarcseconds scale. It is argued that these findings are inconsistent with a standard tidal disruption event (TDE), a binary supermassive black hole (BSMBH), or a changing-look active galactic nucleus (AGN); neither does this object resemble previous observed AGN flares, and disk or jet instabilities are an unlikely scenario. Here, we propose that the behavior of AT\,2021hdr might be due to the tidal disruption of a gas cloud by a BSMBH. In this scenario, we estimate that the putative binary has a separation of sim 0.83 mpc and would merge in sim 7times 10$^4$ years. This galaxy is located at 9 kpc from a companion galaxy, and in this work we report this merger for the first time. The oscillations are not related to the companion galaxy.

The ultraviolet luminosity function of star-forming galaxies between redshifts of 0.4 and 0.6

Abstract We combine ultraviolet imaging of the 13H survey field, taken with the XMM-Newton Optical Monitor telescope (XMM-OM) and the Neil Gehrels Swift Observatory Ultraviolet and Optical Telescope (UVOT) in the UVM2 band, to measure rest-frame ultraviolet 1,500 Å luminosity functions of star-forming galaxies with redshifts z between 0.4 and 0.6. In total the UVM2 imaging covers a sky area of 641 arcmin2, and we detect 273 galaxies in the UVM2 image with 0.4 < z < 0.6. The luminosity function is fit by a Schechter function with best-fit values for the faint end slope $\alpha =-1.8^{+0.4}_{-0.3}$ and characteristic absolute magnitude $M^{*} = -19.1^{+0.3}_{-0.4}$. In common with XMM-OM based studies at higher redshifts, our best-fitting value for M* is fainter than previous measurements. We argue that the purging of active galactic nuclei from the sample, facilitated by the co-spatial X-ray survey carried out with XMM-Newton is important for the determination of M*. At the brightest absolute magnitudes (M1500 < −18.5) the average UV colour of our galaxies is consistent with that of minimal-extinction local analogues, but the average UV colour is redder for galaxies at fainter absolute magnitudes, suggesting that higher levels of dust attenuation enter the sample at absolute magnitudes somewhat fainter than M*.

Towards a complete census of luminous Compton-thick active galactic nuclei in the Local Universe

X-ray surveys provide the most efficient means for the detection of active galactic nuclei (AGNs). However, they do face difficulties in detecting the most heavily obscured Compton-thick AGNs. The BAT detector on board the mission, operating in the very hard 14-195 keV band, has provided the largest samples of Compton-thick AGN in the Local Universe. However, even these flux-limited samples may miss the most obscured sources among the Compton-thick AGN population. A robust way to find these local sources is to systematically study volume-limited AGN samples detected in the IR or the optical part of the spectrum. Here, we utilise a local sample (<100 Mpc) of mid-IR-selected AGNs, unbiased against obscuration, to determine the fraction of Compton-thick sources in the Local Universe. When available, we acquired X-ray spectral information for the sources in our sample from previously published studies. In addition, to maximise the X-ray spectral information for the sources in our sample, we analysed eleven unexplored and observations, for the first time. In this way, we identified four new Compton-thick sources. Our results reveal an increased fraction of Compton-thick AGNs among the sources that have not been detected by BAT of 44 <!PCT!>. Overall, we have estimated a 25-30<!PCT!> share of Compton-thick sources in the Local Universe among mid-IR-selected AGNs. We find no evidence for any evolution of the AGN Compton-thick fraction with luminosity.

Are all models wrong? Falsifying binary formation models in gravitational-wave astronomy using exceptional events

Abstract As the catalogue of gravitational-wave transients grows, several entries appear ‘exceptional’ within the population. Tipping the scales with a total mass of ∼150M⊙, GW190521 likely contained black holes in the pair-instability mass gap. The event GW190814, meanwhile, is unusual for its extreme mass ratio and the mass of its secondary component. A growing model-building industry has emerged to provide explanations for such exceptional events, and Bayesian model selection is frequently used to determine the most informative model. However, Bayesian methods can only take us so far. They provide no answer to the question: does our model provide an adequate explanation for exceptional events in the data? If none of the models we are testing provide an adequate explanation, then it is not enough to simply rank our existing models—we need new ones. In this paper, we introduce a method to answer this question with a frequentist p-value. We apply the method to different models that have been suggested to explain the unusually massive event GW190521: hierarchical mergers in active galactic nuclei and globular clusters. We show that some (but not all) of these models provide adequate explanations for exceptionally massive events like GW190521.

Deep drilling in the time domain with DECam II: characterizing the light curves of candidates in the extragalactic fields

Abstract In this second paper on the DECam deep drilling field (DDF) program we release 2,020 optical gri-band light curves for transients and variables in the extragalactic COSMOS and ELAIS fields based on time series observations with a 3-day cadence from semester 2021A through 2023A. In order to demonstrate the wide variety of time domain events detected by the program and encourage others to use the data set, we characterize the sample by presenting a brief analysis of the light curve parameters such as time span, amplitude, and peak brightness. We also present preliminary light curve categorizations, and identify potential stellar variables, active galactic nuclei, tidal disruption events, supernovae (such as Type Ia, Type IIP, superluminous, and gravitationally lensed supernovae), and fast transients. Where relevant, the number of identified transients is compared to the predictions of the original proposal. We also discuss the challenges of analyzing DDF data in the context of the upcoming Vera C. Rubin Observatory and its Legacy Survey of Space and Time, which will include DDFs. Images from the DECam DDF program are available without proprietary period and the light curves presented in this work are publicly available for analysis.

Discovery of the preferred direction of electric vector position angle rotations in blazars

Blazars are a subclass of active galactic nuclei (AGNs) with a high optical linear polarization that originates in relativistic jets. Polarization parameters such as the degree of polarization (PD) and the electric vector position angle (EVPA) are directly related to the properties of the magnetic field in the jets. A study of the optical polarization of blazars allows conclusions to be drawn about the field geometry, its evolution, and its relation to the emission properties of the blazars. The periods of ordered changes in the electric vector position angle, so-called rotations, are of particular interest. We used a new method to determine EVPA rotations and to estimate their statistical significance with the aim to analyze long-term polarimetric observations of five blazars: OJ 287, S5 0716+71, 3C 454.3, CTA 102, and PG 1553+113. This resultes in the identification of 256 EVPA rotations. We found possible tendencies for the EVPA rotations to occur in a preferred direction in each of these sources: clockwise for OJ 287 and CTA 102, and counterclockwise for the others. The EVPA rotations can be explained by the spiral structure of the magnetic field in the jet. In this case, the observed preferred direction of rotations reflects the global structure of the magnetic field, which can be associated with the direction of rotation of either the black hole ergosphere or the accretion disk.

Eccentric mergers in AGN Discs: Influence of the supermassive black-hole on three-body interactions

Abstract There are indications that stellar-origin black holes (BHs) are efficiently paired up in binary black holes (BBHs) in Active Galactic Nuclei (AGN) disc environments, which can undergo interactions with single BHs in the disc. Such binary-single interactions can potentially lead to an exceptionally high fraction of gravitational-wave mergers with measurable eccentricity in LIGO/Virgo/KAGRA. We here take the next important step in this line of studies by performing post-Newtonian N-body simulations between migrating BBHs and single BHs set in an AGN disc-like configuration, with a consistent inclusion of the central supermassive black hole (SMBH) in the equations of motion. With this setup, we study how the fraction of eccentric mergers varies in terms of the initial size of the BBH semi-major axis relative to the Hill sphere, as well as how it depends on the angle between the BBH and the incoming single BH. We find that the fraction of eccentric mergers is still relatively large, even when the interactions are notably influenced by the gravitational field of the nearby SMBH. However, the fraction as a function of the BBH semi-major axis does not follow a smooth functional shape, but instead shows strongly varying features that originate from the underlying phase-space structure. The phase-space further reveals that many of the eccentric mergers are formed through prompt scatterings. Finally, we present the first analytical solution to how the presence of an SMBH in terms of its Hill sphere affects the probability for forming eccentric BBH mergers through chaotic three-body interactions.

JADES: Primaeval Lyman-α emitting galaxies reveal early sites of reionisation out to redshift z ∼ 9

Abstract Given the sensitivity of the resonant Lyman-α (Lyα) transition to absorption by neutral hydrogen, observations of Lyα emitting galaxies (LAEs) have been widely used to probe the ionising capabilities of reionisation-era galaxies and their impact on the intergalactic medium (IGM). However, prior to JWST our understanding of the contribution of fainter sources and of ionised ‘bubbles’ at earlier stages of reionisation remained uncertain. Here, we present the characterisation of three exceptionally distant LAEs at z > 8, newly discovered by JWST/NIRSpec in the JADES survey. These three similarly bright (MUV ≈ −20 mag) LAEs exhibit small Lyα velocity offsets from the systemic redshift, ΔvLy$α$ ≲ 200 km s−1, yet span a range of Lyα equivalent widths (15 Å, 31 Å, and 132 Å). The former two show moderate Lyα escape fractions ($f_\text{esc, {Ly$\alpha $}} \approx 10\%$), whereas Lyα escapes remarkably efficiently from the third ($f_\text{esc, {Ly$\alpha $}} \approx 72\%$), which moreover is very compact (half-light radius of 90 ± 10 pc). We find these LAEs are low-mass galaxies dominated by very recent, vigorous bursts of star formation accompanied by strong nebular emission from metal-poor gas. We infer the two LAEs with modest fesc, Ly$α$, one of which reveals evidence for ionisation by an active galactic nucleus, may have reasonably produced small ionised bubbles preventing complete IGM absorption of Lyα. The third, however, requires a ∼3 physicalMpc bubble, indicating faint galaxies have contributed significantly. The most distant LAEs thus continue to be powerful observational probes into the earlier stages of reionisation.

A hidden Active Galactic Nuclei population: the first radio luminosity functions constructed by physical process

Abstract Both star formation (SF) and Active Galactic Nuclei (AGN) play an important role in galaxy evolution. Statistically quantifying their relative importance can be done using radio luminosity functions. Until now these relied on galaxy classifications, where sources with a mixture of radio emission from SF and AGN are labelled as either a star-forming galaxy or an AGN. This can cause the misestimation of the relevance of AGN. Brightness temperature measurements at 144 MHz with the International LOFAR telescope can separate radio emission from AGN and SF. We use the combination of sub-arcsec and arcsec resolution imaging of 7,497 sources in the Lockman Hole and ELAIS-N1 fields to identify AGN components in the sub-arcsec resolution images and subtract them from the total flux density, leaving flux density from SF only. We construct, for the first time, radio luminosity functions by physical process, either SF or AGN activity, revealing a hidden AGN population at L144MHz<1024 W Hz−1. This population is 1.56±0.06 more than expected for 0.5 < z < 2.0 when comparing to RLFs by galaxy classification. The star forming population has only 0.90±0.02 of the expected SF. These “hidden” AGN can have significant implications for the cosmic star formation rate and kinetic luminosity densities.

Depolarization and Faraday effects in AGN Jets

ABSTRACT Radio interferometric observations of active galactic nuclei (AGN) jets reveal the significant linear polarization of their synchrotron radiation that changes with frequency due to the Faraday rotation. It is generally assumed that such depolarization could be a powerful tool for studying the magnetized plasma in the vicinity of the jet. However, depolarization could also occur within the jet if the emitting and rotating plasma are cospatial (i.e. the internal Faraday rotation). Burn obtained very simple dependence of the polarization on the wavelength squared for the discrete source and resolved slab that is widely used for interpreting the depolarization of AGN jets. However, it ignores the influence of the non-uniform large-scale magnetic field of the jet on the depolarization. Under the simple assumptions about the possible jet magnetic field structures, we obtain the corresponding generalizations of Burn’s relation widely used for galaxies analysis. We show that the frequency dependences of the Faraday rotation measure and polarization angle in some cases allow to estimate the structures of the jets magnetic fields.

Searching for similarities in the accretion flow of Seyfert 1 galaxies and cataclysmic variables based on the flare profiles of IRAS 13224-3809, 1H 0707-495, Mrk 766, and MV Lyr

We studied the fast variability of three selected active galactic nuclei (AGNs), IRAS\,13224-3809, 1H\,0707-495, and Mrk\,766, and the cataclysmic variable MV\,Lyr, which were observed by the and spacecrafts, respectively. Our goal is to search for the common origin of the variability and to test the so-called sandwich model, in which a geometrically thick corona surrounds a geometrically thin disc. We studied the substructures of the averaged flare profiles. The flare profile method identifies individual flares in the light curve, and averages them. The direct fitting of the profile substructures identified individual characteristic frequencies that are seen in standard power density spectra (PDS) as a break frequency or quasi-periodic oscillation. The credibility of the flare profile substructures is demonstrated by comparison with the autocorrelation function. We found that the flare profiles of AGNs are similar to those of a cataclysmic variable in the low state. We explain this as a consequence of a truncated inner disc in a sandwich model. The same scenario is also able to explain the characteristic break frequencies in X-ray PDS, which are not seen in the optical. We also searched for substructures in the flare profile of IRAS\,13224-3809. In addition to a permanently present main flare, we found that a transient side-lobe appears before the main flare and is only seen in a high-flux period. The complex flare profile of this AGN suggests that an additional source of X-rays appears during the high-flux period. We propose a scenario in which an accretion flow fluctuation enters the sandwich corona and propagates further to some very central part of the accretion disc.

Swift-XRT follow-up analysis of unidentified hard X-ray sources. Searching for soft X-ray counterparts of unidentified hard X-ray sources

It has been established that the sources contributing to the cosmic X-ray background (CXB) emission are mainly nearby active galactic nuclei (AGNs), in particular those that are obscured. Thus, it is important to fully identify the hard X-ray sky source population to accurately characterize the individual contribution of different AGNs to the overall CXB emission. We present a follow-up analysis of all 218 sources marked as unidentified in our previous revision of the third release of the Palermo Swift -BAT hard X-ray catalog (3PBC) based on our multifrequency classification scheme. These 218 sources were classified as unidentified in our previous analyses because they lacked an assigned low-energy counterpart. We searched for soft X-ray counterparts of these 218 3PBC sources in archival Swift -XRT observations obtained between January 1, 2005, and August 1, 2018. In particular, we found 1213 archival Swift -XRT observations for 192 of the 218 unidentified sources. We find 93 possible Swift -XRT counterparts within the Swift -BAT positional uncertainty regions. They correspond to 73 3PBC sources, 60 of which have only a single Swift -XRT detection; the rest have multiple detections. We present all the detected possible counterparts of the as-of-yet-unidentified hard X-ray sources to the community as a catalog for future spectroscopic follow-up targets, together with a short catalog of our classification of the ten sources for which there were available spectra.

Crimson Behemoth: A massive clumpy structure hosting a dusty AGN at z=4.91

Abstract The current paradigm for the co-evolution of galaxies and their supermassive black holes postulates that dust-obscured active galactic nuclei (AGNs) represent a transitional phase towards a more luminous and unobscured state. However, our understanding of dusty AGNs and their host galaxies at early cosmic times is inadequate due to observational limitations. Here, we present JWST observations of CID-931, an X-ray-detected AGN at a spectroscopic redshift of $z_{\rm spec}=4.91$. Multiband NIRCam imaging from the COSMOS-Web program reveals an unresolved red core, similar to JWST-discovered dusty AGNs. Strikingly, the red core is surrounded by at least eight massive star-forming clumps spread over ${1{^{\prime \prime}_{.}}6} \approx 10\,\,{\rm kpc}$, each of which has a stellar mass of $10^9$–$10^{10}\, M_{\odot }$ and a radius of $\sim$0.1–1 kpc. The whole system amounts to $10^{11}\, M_{\odot }$ in stellar mass, higher than typical star-forming galaxies at the same epoch. In this system, gas inflows and/or complex merger events may trigger clump formation and AGN activity, thus leading to the rapid formation of a massive galaxy hosting a supermassive black hole. Future follow-up observations will provide new insights into the evolution of the galaxy–black hole relationship during such transitional phases in the early universe.

Layout optimization and Performance of Large Array of imaging atmospheric Cherenkov Telescope (LACT)

Abstract Large Array of imaging atmospheric Cherenkov Telescope (LACT) is an array of 32 Cherenkov telescopes with 6-meter diameter mirrors to be constructed at the LHAASO site. In this work, we present a study on the layout optimization and performance analysis of LACT. We investigate two observation modes: large zenith angle observations for ultra-high energy events and small zenith angle observations for lower energy thresholds. For large zenith angles (60°), simulations show that an 8-telescope subarray can achieve an effective area of $3 ~\rm km^2$ and excellent angular resolution. For small zenith angles, we optimize the layout of 4-telescope cells and the full 32-telescope array. The threshold of the full array is about $200~\rm GeV$, which is particularly crucial for studying transient phenomena, including gamma-ray bursts (GRBs) and active galactic nuclei (AGNs). This study provides important guidance for the final LACT layout design and performance estimates under different observational conditions, demonstrating LACT's potential for deep observations of ultra-high energy \gray sources and morphological studies of PeVatrons, as well as time-domain \gray astronomy.

Discovering Changing-Look AGN in the 6dF Galaxy Survey using ATLAS Light curves

Abstract Changing-Look Active Galactic Nuclei (CLAGN) are characterised by extreme variations in line emission over short timescales, mostly affecting broad Hβ lines. While a few hundred CLAGN are known, a complete sample of turn-on CLAGN is still elusive. Here, we present a search for turn-on CLAGN in a complete sample of galaxies, using archival spectra and recent light curves. We obtained light curves from the Asteroid Terrestrial Impact Last Alert System (ATLAS) for 16 232 emission line galaxies, including both star-forming and active galaxies, at z < 0.1 with spectra from the Six-degree Field Galaxy Survey (6dFGS). We first establish typical variability behaviour for different AGN types, as recorded between 2001 and 2009, and then select outliers from the bulk behaviour as CLAGN candidates. We obtain new spectra for the candidates and identify 12 new turn-on CLAGN (appearing broad Hβ line) and 19 new turn-off CLAGN (disappearing broad Hβ line). We may have missed AGN that changed and reverted their state over the 15−20 years since 6dFGS spectra were taken, and thus our CLAGN rates of 1.7% for turn-on and 9.6% for turn-off are lower limits. The turn-on rate is naturally much lower as the type 1.9/2 sample is dominated by obscured AGN due to orientation, which are not expected to change. However, the number of turn-on (27) and turn-off (24) CLAGN we find are similar, suggesting that our parent AGN sample is reasonably complete in our search volume at z < 0.1.

Mapping AGN winds: A connection between radio-mode AGNs and the AGN feedback cycle

We present a kinematic analysis based on the large integral field spectroscopy (IFS) dataset of SDSS-IV MaNGA (Sloan Digital Sky Survey/Mapping Nearby Galaxies at Apache Point Observatory; ∼10 000 galaxies). We have compiled a diverse sample of 594 unique active galactic nuclei (AGNs), identified through a variety of independent selection techniques, encompassing radio (1.4 GHz) observations, optical emission-line diagnostics (BPT), broad Balmer emission lines, mid-infrared colors, and hard X-ray emission. We investigated how ionized gas kinematics behave in these different AGN populations through stacked radial profiles of the [O III] 5007 emission-line width across each AGN population. We contrasted AGN populations against each other (and non-AGN galaxies) by matching samples by stellar mass, [O III] 5007 luminosity, morphology, and redshift. We find similar kinematics between AGNs selected by BPT diagnostics compared to broad-line-selected AGNs. We also identify a population of non-AGNs with similar radial profiles as AGNs, indicative of the presence of remnant outflows (or fossil outflows) of past AGN activity. We find that purely radio-selected AGNs display enhanced ionized gas line widths across all radii. This suggests that our radio-selection technique is sensitive to a population in which AGN-driven kinematic perturbations have been active for longer durations (potentially due to recurrent activity) than in purely optically selected AGNs. This connection between radio activity and extended ionized gas outflow signatures is consistent with recent evidence that suggests radio emission (expected to be diffuse) originated due to shocks from outflows. We conclude that different selection techniques can trace different AGN populations not only in terms of energetics but also in terms of AGN evolutionary stages. Our results are important in the context of the AGN duty cycle and highlight integral field unit data’s potential to deepen our knowledge of AGNs and galaxy evolution.